Fuel ignition apparatus for an afterburner in the bypass duct of a turbojet engine



Aug. 19; 1958 J. K. BROWN FUEL IGNITION AP PARATUS FOR AN AFTERBURNER IN THE BYPASS DUCT OF A TURBOJET ENGINE Filed June 21, 1956 xlllrl Illll I. l!

INVENTOR John K. Brown ATTORNEY United States Patent Ofiice FUEL IGNITION APPARATUS FOR AN AFTER- BURNER IN THE BYPASS DUCT OF A TURBO- JET ENGINE John K. Brown, Sharon Hill, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Application June 21, 1956, Serial No. 592,988

7 Claims. (Cl. 60-35.6)

This invention relates to fuel ignition apparatus, more particularly to fuel ignition apparatus wherein a hotstreak or pilot flame of short duration ignited by flame in a first fuel combustion system is provided for igniting the fuel in a second fuel combustion system; and has for an object to provide an improved hotstreak fuel ignition apparatus for igniting the fuel in the second fuel combustion system when the two fuel combustion systems are separated from each other by Wall structure.

Hotstreak fuel ignition apparatus has been found highly advantageous and more reliable than electrical spark fuel ignition apparatus for igniting the afterburners of aviation turbojet engines, since in the event of failure of the electrical system the afterburner may still be ignited. However, in turbofan engines and similar turbojet engines, wherein it is desired to augment the propulsive thrust of the afterburner in the central gas passageway by providing an afterburner in the bypass duct, the problem becomes more complex due to the dividing wall between the bypass duct and the central passageway.

In view of the above, it is a further object of the invention to provide an improved hotstreak fuel ignition device for igniting an afterburner in the bypass duct of a turbofan jet engine.

A more specific object of the invention is to provide a hotstreak fuel ignition device of the above type which is simple in structure, may be economically and expeditiously fabricated, and which is durable and reliable in operation.

In aviation turbojet engines, the gas turbine is driven by gaseous products of combustion provided by primary fuel combustion structure and the exhaust gases are ejected through the rear exhaust nozzle of the engine to provide the forward propulsive thrust. Such engines may be provided with secondary fuel combustion structure, termed afterburners, interposed between the turbine and the exhaust nozzle for augmenting the thrust of the engine for brief intervals (such as when a sudden burst of speed is desired) by increasing the volume and/ or the velocity of the exhaust gases. Afterburners of this type have been ignited by hotstreak" fuel ignition apparatus comprising a fuel injection nozzle extending into the primary combustion apparatus for delivering an excess quantity of fuel thereto for a brief time interval, suificient to cause an elongated flame to extend from the primary combustion structure to the secondary cornbustion structure, and timed to ignite the fuel being injected therein. Neal Patent No. 2,640,316, issued June 2, 1953, and assigned to the assignee of this invention is representative of such art.

In accordance with the invention, wherein it is desired to provide a hotstreak fuel ignition device for an additional fuel combustion structure (bypass afterburner) disposed in the bypass duct of a turbofan engine, a communicating opening is provided between the primary fuel combustion structure and the bypass duct. A valve structure is provided which is-normally in a position blocking the opening but movable to the unblocking position by a fluid pressure responsive mechanism. A hotstreak fuel ignitor nozzle carried bythe valve structure is connected to a source of fuel supply in such. a manner that as fuel is delivered to the hotstreak ignitor nozzle, the valve structure is actuated to the unblocking position by the fluid pressure responsive mechanism, thereby permitting ignition of the fuel issuing from the hotstreak ignitor nozzle by the flame from the primary combustion structure. from the hotstreakf ignitor nozzle extends into the bypass duct a distance suflicient to ignite the fuel being injected into the bypass afterburner. After ignition of the bypass afterburner is attained, fuel to the hotstreak ignitor nozzle is terminated and the subsequent reduction in fuel pressure allows the valve structure to-return: to its original blocking position.

These and other objects are elfected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a diagrammatic axial sectional view of an aviation turbofan engine having the invention incorporated therein; j

Fig. 2 is an enlarged fragmentary sectional view of the fuel ignition structure of Fig. 1, shown in the igniting position; Fig. 3 is a sectional view taken on lines -III-III of Fig. 2;

Fig. 4 is a perspective View of the fuel ignition struc-;

ture in the igniting position; and

Fig. 5 is a view similar to Fig. 2 but showing the fuel ignition structure in the inactive position.

it Referring to the drawing in detail, in Fig. 1 thereris shown an aviation jet engine of the turbofan type comprising a low pressure compressor rotor 11, a high pressure compressor rotor 12, a high pressure turbine rotor 13 and. a low pressure turbine rotor 14. The highpres sure turbine rotor 13 is connected to the high pressure compressor rotor 12 by a hollow shaft throughwhich extends an inner shaft 16 connecting the low pressure turbine rotor 14 to the low pressure compressor rotor 11.

The shafts 15 and 16 are supported by suitable bearings.

17 and 18 for independent rotation,

Between the high pressure compressor rotor 12 and. the high pressure turbine rotor 13'there is interposed a: primary fuel combustion structure 19, which, as illustrated, may be of the annular type comprising concentric inner and outer walls 20 and 21, respectively, defining an annular combustion chamber 22 and provided with suitable fuel injecting means 23 and electrical ignition means 23a.

The high pressure compressor rotor 12, the primary combustion structure 19, the high pressure turbine rotor 13 and the low pressure turbine rotor 14 are received 1 within a tubular central shell structure 24 which together with concentric, inner core structure 25, provides a central annular passageway 26 for flow of gases. The low pres-' sure compressor rotor is received within an elongated outer tubular shell structure 27, encompassing the central shell structure 24. and providing an air inlet 28 and an exhaust outlet 29. The outer shell 27 is of larger diameter than the central shell 24 and together therewith defines an annular passageway or bypass duct 30 which is in communication with the central gas passageway 26 at the air inlet to the high pressure compressor rotor 12.

Thus, as Well known in the art, the hot gaseous products of combustion generated within the primary combustion structure 19 by combustion of fuel, admitted thereto by the fuel injecting means 23 and ignited by the ignition means 23a, motivate the high pressure turbine rotor 13 and low pressure turbine rotor 14 which, in turn, drive the high pressure compressor rotor 12 and the low pres- Patented Aug. 19, 1958 The plume of flame,

sure compressor rotor 11 which provide the compressed air required for combustion. The gases exhausted from the low pressure turbine rotor are then ejected through the exhaust outlet 29 to provide a propulsive thrust, as well known in the art.

It-will be noted that some of the compressed air from the low pressure compressor rotor 11 flows through the bypass duct 30 and joins the hot exhaust gases immediately upstream of the exhaust outlet 29, mixing therewith before final ejection.

In accordance with the usual practice, an auxiliary fuel combustion structure or main afterburner 31 comprising an annular fuel injecting manifold 32 and suitable flameholdingstructure 33 may be provided in the exhaust collector portion 24a of the central shell structure 24 for augmenting the volume and/or velocity of the hot gases exhausted by the low pressure turbine rotor 14. The afterburner 31 is employed for brief intervals when a short burst of additional power is desired. Hence, it readily lends itself to ignition by hotstreak ignition apparatus which may take the form more fully described and claimed in Neal Patent No. 2,640,316, previously mentioned.

An additionally auxiliary fuel combustion structure 34 (hereinafter termed the bypass afterburner) is also provided in the bypass duct 30 for augmenting the volume and/or velocity of the bypass air flow. The bypass afterburner 34 is similarly provided with an annular fuel injecting manifold 35 and suitable flameholding structure 36.

A fuel control system 40 for the engine is schematically illustrated in Fig. 1, including a source of fuel 41, a' supply conduit 42 connected to a main fuel pump 43 and a delivery conduit 44 connected to the primary fuel injecting means 23 through a fuel metering control mechanism 45. The fuel metering control mechanism 45 is regulated by a throttle lever 46 (shown in the oif position) movable through a non-afterburning range from off to the maximum non-afterburning position 47.

A'hotstreak fuel ignition control system 48 for igniting themain afterburner 31 may typically comprise a hotstreak fuel nozzle 49 disposed in the primary combustion structure 19 and fed by fuel delivered thereto by a branch supply conduit 50 (connected to the fuel source 41) an afterburner fuel pump 51, an afterburner fuel control mechanism 52 and a branch'delivery conduit 53a, 53b having a hotstreak ignitor control mechanism 55 interposed therein. Fuel metered by the afterburner fuel control mechanism 52 is delivered to the main afterburner fuel manifold 32 by a delivery conduit 56.

The hotstreak ignition control system 48 is controlled by the movable throttle lever 46, upon movement thereof into the afterburning range designated by numeral 57. Hence, in a known manner, when the throttle lever 46 is moved into the afterburning range 57, the afterburner fuel pump 51 is energized, thereby delivering fuel to the afterburner fuel control mechanism 52, from whence it is delivered in metered quantity to the main afterburner fuel manifold 32. Concomitantly, therewith fuel is delivered by conduit 53a to the hotstreak ignitor control mechanism 55 and thence by conduit 53b to the hotstreak fuel nozzle 49 for a brief period, on the order of a few seconds. As the fuel issues from the hotstreak fuel nozzle 49 into the primary combustion chamber 22, it is immediately ignited by the combustion flame therein and produces a streak of flame which is swept downstream through the turbine rotors 13 and 14 and into the main afterburner 31, where it ignites the fuel being injected therein by the fuel manifold 32. At the end of the brief ignition period, the ignitor control mechanism 55 terminates fuel flow to the hotstreak ignitor nozzle 49.

Although the above described hotstreak ignitor 49 is adequate for igniting the main afterburner 31, it is inadequate for igniting the bypass afterburner 34, since the bypass afterburner is separated from the main afterburner by the central shell structure 24.

In accordance with the invention, there is provided a novel hotstreak fuel ignition structure, generally desig nated 60, for igniting the bypass afterburner 34 which, as best shown in Figs. 2-5 inclusive comprises a hotstreak fuel ignitor nozzle 61 disposed adjacent a pair of aligned openings 62 and 63 formed in the outer wall 21 of the main fuel combustion structure and the central shell structure 24, respectively. A leaf valve member 64 is provided for blocking and unblocking the opening 62, while a leaf valve member 65 is provided for blocking and unblocking the opening 63. The valve member 65 is hingeably supported at one end by a conventional pintle 66. However, the valve 64 is hingeably supported at its mid-point by a hollow pintle 67 which is plugged at one end as indicated at 68 and has its other end in fluid communication with the fuel conduit 53b. A yieldable fluid conducting member, for example a bellows 69, is interposed between the conduit 53b and an offset terminal portion 67a of the hollow pintle 67 to permit relative movement between the rigidly supported conduit 53b and the rotatable pintle 67, for a purpose which will subsequently be described.

The hollow pintle 67 has mounted thereon a crank arm 70 which is operatively connected by a connecting rod 71 to one end of a fluid pressure actuated mechanism such as a bellows 72. The bellows 72 is connected to the fuel conduit 53b by a short branch conduit 73.

The valve member 64 has mounted thereon a gutter or V-shaped trough member 75 extending transversely of the pintle 67. The ignitor nozzle 61 is carried by the.

valve member 64 and has its inlet end in communication with the hollow pintle 67 and its outlet end 61a extending through the trough member 75 and facing the longitudinal axis thereof.

The valve member 64 is further provided with an actuator arm 76 extending toward the valve member 65 and provided with a contacting roller 77, so that the valves 64 and 65 are jointly operable.

In operation, when the throttle lever 46' is moved into the afterburning range 57, as mentioned heretofore, the afterburner fuel pump 51 is energized to provide fuel to the afterburner fuel control 52, so that fuel in metered quantity is fed through conduit 56 to the bypass afterburner manifold 35. concomitantly therewith, the hotstreak ignitor control mechanism 55 is energized to provide flow of liquid fuel through the conduit 53b, the bellows 69, hollow pintle 67 and the hotstreak nozzle 61. As the actuating bellows 72 is filled with fuel, it is elongated by the fuel pressure, thereby rotating the crank arm 70 and the pintle 67 in clockwise direction, as viewed in Fig. 4, and moving the valve member 64 to the open or unblocking position. During opening movement of the valve member 64, the actuating arm 76 urges the valve member 65 to its open position, so that fluid communication between the main combustion chamber 22 and the bypass duct 30 is initiated through the openings 62 and 63.

As the flame and highly pressurized hot gases from the main combustion chamber 22 are swept through the openings 62, 63 into the bypass duct, the fuel issuing from the hotstreak nozzle 61 is ignited and swept along the trough 75 into the bypass duct. The resulting hotstreak or flame is of suflicient length to extend downstream to the region immediately surrounding the fuel manifold 35 of the bypass afterburner 34, thereby initiating ignition of the fuel issuing therefrom, The resulting flame is thereupon anchored upon the flame holding means 36 in the usual manner.

After fuel flow through the conduit 53b for the starting cycle is terminated by the hotstreak ignitor mechanism 55, the fuel pressure in the actuating bellows 72 is reduced, whereupon the bellows 72 returns to its original contracted condition and moves the valves 64 and 65 to their blocking positions.

It will now be seen that the invention provides a simple yet reliable hotstreak igniting mechanism for initiating ignition of an afterburner in a duct separated from the main fuel combustion apparatus by wall or partition structure.

It will also be seen that the hotstreak igniting structure is self-sufficient, since the fuel for the hotstreak nozzle 61 provides the motive power for moving the valves 64 and 65 to the unblocking position. This arrangement insures accurate synchronization of movement of the valves 64 and 65 with the issuance of fuel from the hotstreak nozzle 61.

Although in the arrangement illustrated, the afterburner hotstreak ignition system has been shown as of the type in which the main afterburner 31 and the bypass afterburner 34 are jointly operable by a common afterburner fuel control 52 and hotstreak ignitor con trol 55, it will be understood that this arrangement is not essential to the invention and that the afterburners may be operable separately by duplicate controls, if desired.

Only one hotstreak fuel ignition structure 60 has been illustrated for igniting the bypass afterburner 34. However, if desired, two or more such structures circumferentially spaced about the inner shell 24 may be provided.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What is claimed is:

1. In fuel combustion apparatus including a first fuel combustion structure, a second fuel combustion structure, partition structure separating said first and second fuel combustion structures and means for igniting fuel in said first fuel combustion structure; hotstreak fuel ignition structure for igniting the fuel in said second fuel combustion structure comprising means defining an opening in said partition structure, a valve member for blocking said opening, a hotstreak" fuel ignitor nozzle disposed adjacent said opening, means including a fuel conduit for initiating flow of fuel to said fuel ignitor nozzle for a short time period, means for concomitantly initiating flow of fuel to said second fuel combustion structure and means responsive to fuel pressure in said fuel conduit for moving said valve member in opening direction.

2. In fuel combustion apparatus including inner and outer concentric shells defining a first fuel combustion structure, wall structure disposed within said inner shell and defining a second fuel combustion structure and means for igniting fuel in said second fuel combustion structure; hotstreak fuel ignition structure for igniting the fuel in said first fuel combustion structure subsequent to ignition of fuel in said second fuel combustion structure comprising means defining a first opening in said wall structure, means defining a second opening in said inner shell in registry with said first opening, valve structure for blocking and unblocking one of said openings, a hotstreak fuel ignitor nozzle disposed adjacent said openings, means including a fuel conduit for initiating fiow of fuel to said fuel ignitor nozzle for a short time period, means for concomitantly initiating flow of fuel to said first fuel combustion structure, and means responsive to fuel pressure in said fuel conduit for moving said valve structure in unblocking direction.

3. In a turbojet engine having an inner shell housing a compressor, a turbine for driving said compressor and primary fuel combustion structure interposed between said compressor and said turbine; said primary fuel combustion structure being defined by wall structure and having means for igniting fuel therein; and an outer shell disposed in spaced concentric relation with said inner shell and together therewith defining an annular bypass duct, said bypass duct having a secondary fuel combustion portion: hotstreak fuel ignition structure for igniting the fuel in said secondary combustion portion subsequent to ignition of fuel in said primary fuel combustion structure comprising means defining a first opening in said wall structure, a second opening in said inner shell in registry with said first opening, valve structure for blocking and unblocking one of said openings, a hotstreak fuel ignitor nozzle disposed adjacent said openings, means including a fuel conduit for initiating flow of fuel to said fuel ignitor nozzle for a short time period, means for concomitantly initiating flow of fuel to said secondary fuel combustion portion, and means responsive to fuel pressure in said fuel conduit for moving said valve structure in unblocking direction.

4. In fuel combustion apparatus including a first fuel combustion structure, a second fuel combustion structure, partition structure separating said first and second fuel combustion structures and means for igniting fuel in said first fuel combustion structure; hotstreak fuel ignition structure for igniting the fuel in said second fuel combustion structure comprising means defining an opening in said partition structure, a valve member for blocking said opening, a hotstreak fuel ignitor nozzle disposed adjacent said opening, pivotal support means for said valve member, means including a fuel conduit for initiating flow of fuel to said fuel ignitor nozzle for a short time period, means for concomitantly initiating fiow of fuel to said second fuel combustion structure and means responsive to fuel pressure in said fuel conduit for moving said valve member in opening direction, said pressure responsive means including a movable abutment,

and said movable abutment being connected to said pivotal support means.

5. In fuel combustion apparatus including a first fuel combustion structure, a second fuel combustion struc ture, partition structure separating said first and second fuel combustion structures and means for igniting fuel in said first fuel combustion structure; hotstreak fuel ignition structure for igniting the fuel in said second fuel combustion structure comprising means defining an opening in said partition structure, a valve member for blocking said opening, a hotstreak fuel ignitor nozzle carried by said valve member and disposed adjacent said opening, said valve member and said fuel ignitor nozzle being jointly movable, means including a fuel conduit for initiating flow of fuel to said fuel ignitor nozzle for a short time period, means for concomitantly initiating flow of fuel to said second fuel combustion structure and means responsive to fuel pressure in said fuel conduit for moving said valve member in opening direction, said pressure responsive means including a movable abutment in communication with said fuel conduit and operatively connected to said valve member.

6. In fuel combustion apparatus including inner and outer concentric shells defining a first fuel combustion structure, wall structure disposed within said inner shell and defining a second fuel combustion structure, and means for igniting fuel in said second fuel combustion structure; hotstreak fuel ignition structure for igniting the fuel in said first fuel combustion structure subsequent to ignition of fuel in said second fuel combustion structure comprising means defining a first opening in said wall structure, means defining a second opening in said inner shell in registry With said first opening, valve structure for blocking and unblocking one of said openings, a hotstreak fuel ignitor nozzle carried by said valve structure and disposed adjacent said openings, means including a first fuel conduit for initiating flow of fuel to said fuel ignitor nozzle for a short time period, means for concommitantly initiating flow of fuel to said first fuel combustion structure, means responsive to fuel pressure in said first fuel conduit for moving said valve structure in unblocking direction, a second fuel conduit for pivotally supporting said valve structure, said second fuel conduit beingconnected to said fuel ignitor nozzle and in communication with said first fuel conduit, and flexible fluid transmitting means interposed between said first fuel conduit and said second fuel conduit.

7. In fuel combustion apparatus including inner and outer concentric shells defining a first fuel combustion structure, Wall structure disposed Within said inner shell and defining a second fuel combustion structure, and means for igniting fuel in said second fuel combustion structure; hotstreak fuel ignition structure for igniting 3 the fuel in said first fuel combustion structure subsequent to ignition of fuel in said second fuel combustion structure comprising means defining a first opening in said wall structure, means defining a second opening in said inner shell in registry with said first opening, valve structure for blocking and unblocking one of said openings, a hotstreak fuel ignitor nozzle carried by said valve n o structure and disposed adjacent said openings, means including a first fuel conduit for initiating flow of fuel to said fuel ignitor nozzle for a short time period, means for concomitantly initiating flow of fuel to said first fuel combustion structure, means including an abutment movable in response to fuel pressure in said first fuel conduit for moving said valve structure in unblocking direction, a second fuel conduit for pivotally supporting said valve structure, said second fuel conduit being connected to said fuel ignitor nozzle and in communication with said first fuel conduit, said abutment being operatively connected to the second fuel conduit, and flexible fluid transmitting means interposed between said first fuel conduit and said second fuel conduit.

No references cited. 

